1. Field of Invention
The present invention relates to a hose roller pump comprising a stator, a rotor and a rotor drive, with the rotor including hose rollers.
2. Description of the Prior Art
In such hose roller pumps, a hose is inserted between the rotor and the hose roller path of the stator and is pressed by the hose rollers in each case against the hose roller path so that liquid is pumped through the hose by the rotation of the rotor and thus the revolving movement of the hose rollers. Such hose roller pumps find a plurality of uses in particular in medical engineering and are used especially in dialysis, in particular in hemodialysis or peritoneal dialysis, for the pumping of medical liquids such as dialysis liquid or blood.
A simple base type still dominates among the hose roller pumps for disposable pump hoses established on the market for medical engineering. This long known base form of a hose roller pump on which the hose roller pump of the present invention is also based will now be explained in more detail. The reference numerals correspond in this connection to the reference numerals also used in FIGS. 1 to 8 which show the hose roller pump of the present invention, with reference likewise being made to these Figures for the explanation of basic functions which are used in the hose roller pump of the present invention and equally in the prior art.
In this connection, the rotor comprises the rotationally driven hub shell 4 at which, as a rule, two rotating wings 5 are supported radially outwardly assisted by a spring, with a respective hose roller 9 being fastened to each of the outer ends of said wings which attempts to squeeze the hose 2 peripherally against the hose roller track. The hose roller track is a component of the fixed-position part of the hose roller pump which is often called a pump bed or stator 1. FIG. 1 explains the functional division of the hose roller running track into three different segments. The middle segment 17 (occlusion region) covers approximately 180 degrees and represents a cylindrical surface. The hose is completely occluded by the hose rollers in this segment. The segments 18 (transition regions) adjoining in the manner of a mirror image extend over approximately 20 . . . 30 degrees. In this region, the radius of the roller running track increases continuously without the pump hose moving out of occlusion. The wings rather still follow the increase in radius until the point is reached toward the end of the transition region at which the wings run onto abutments which are arranged between the hub shell and the wing and bound the further radial outward movement of the wings and hose rollers. Such abutments are provided at each hose roller pump and are not shown in the Figures. In the last segment 19 (opening region) which adjoins at both sides in the manner of a mirror image, the radius of the roller running track increases further while the wing remains at the said abutment until the pump hose has moved completely out of engagement by the hose rollers still before the start of the pump bed mouth region 20. In this mouth region, the pump hose moves into the pump bed and leaves it again. The aforesaid wing abutments have the additional object of preventing the hose rolls from striking the hose roller track when the pump hose has been removed. For this purpose, the abutments are set so that they permit a residual gap of approximately 1 mm between the hose roller and the roller running track, much less than twice the wall thickness of the occluded pump hose (occlusion condition).
To avoid the unwanted departure of the pump hose from the pump bed, the pumps usual on the market have a plurality of hose guiding wings 21 which project radially outwardly from the hub shell like individual prongs and end in front of the hose roller running track at a low end face distance of approximately 1 to 3 mm. The hose guiding wings are usually equipped with rotatable rollers to avoid friction and wear and play an important role on the threading in and out of the pump hose. If the rotor is brought into a rotary position in which a hose guide wing faces in the direction of the opening of the pump mouth the free spaces at both sides of the adjacent positions of the pump bed mouth are thus sufficient for the operator to be able to introduce the half of the pump hose at the inflow side so far in the direction of the pump bed base that the hose guide wing combs over the hose in the following thread-in rotary movement of the rotor and sweeps it into the pump bed. Since the hose rollers are moved out up to the abutments with customary hose pumps, the hose guide wings have to exert so much force on the hoses as necessary to urge them into the gap between the hose roller and the roller running track, said gap initially being approx. 1 mm wide, and to bring the wings to pivot in against the force of the springs until the pump hose is completely threaded in and is rolled over by the two hose rollers. The elastomeric pump hose is deformed by this exertion of force and attempts to penetrate into the gap between the hose roller track and the end face of the hose guide wings. To preclude this reliably, the spacing between the end face of the hose guide wings and the hose roller track may only lie between approximately 2 . . . 3 mm in the conventional hose pumps. Equally, the rounding radius of the guide roll toward the end face may not be much larger than 1 mm because a sufficient condition for the clamping of the pump hose on the thread-in procedure would also then arise. Occasionally, the pump hose is still clamped on the threading in, which as a rule results in damage to the hose and requires the replacement of the pump hose. The diagonal urging of the pump hose into the desired position can also occasionally be associated with damage to the pump hose which is usually due to the local overstrain on the passing of the end edges of the hose rollers. A further failure can occur when the pump hose is not introduced sufficiently deeply by the operator so that the end face of the hose guide wing disposed most closely can receive the hose on the approach to the hose roller track and can damage it. On such an incident, the ball bearing of the rotor shaft on the output side can also be overstrained, which can result in pump failure days or months later. A third and much more critical possible failure consists of the operator not removing his finger from the pump bed in time and there thereby being the danger of injury due to the collision with the hose guide wing or with the hose rollers.
A similar procedure takes place on the same side of the pump bed mouth on the thread out of the pump hose: with a stationary pump in an angular position as before, the end of the pump hose at the inflow side must be raised so far out of the pump bed that, after the switching back of the rotor movement, those guide wing disposed most closely combs under the pump hose and peels it out of the pump bed in a similar fashion to a tire lever movement. Corresponding failures as during the threading in can also occur here.
Due to the disadvantages described above of the manually equipped hose pumps, a semi-automatic mechanism was introduced with dialysis machines which works as follows: the pump hose is held at both sides in a component called a clip which is introduced into the pump mouth region in a latching manner by the person on the insertion. The pump hose thereby comes into the position which is required for the subsequent threading in and a position report contact is triggered. In this manner, the operator can remove the hands and actuate the starting button for the following automatic threading in. The threading out of the pump hose segment takes place automatically in that the rotor stops in the thread-out start position and a lifting actuator raises the clip with a tilt movement so far out of the pump mouth region as is required for the following automatic threading out.
The mechanism just described still has the disadvantage that the pump housing is exposed to strong mechanical strains on the threading in and out and that small errors in the coordination of the geometrical and force-related ratios between the machine and the pump hose segment can result in problems. The mechanism cannot be used in some applications since it necessarily requires a tiling of the pump hose segment at the start of the thread-out phase which cannot be carried out, for example, with cassette systems having a plurality of hose pump segments. A further disadvantage of the mechanism just described consists in the increased space requirements and in the increased manufacturing costs since an additional electrically or pneumatically driven linear unit for the lifting of the pump hose segment out of the pump bed is added to the original rotor mechanism.
It has therefore partly been attempted for the facilitating of the hose change to split the pump hose bed into a plurality of parts and to move them radially outwardly to be able to insert or remove the hose better. In this connection, the problem arises, however, that the joints of the segmented hose roller track are rolled over continuously during pumping so that problems in the pump function (such as e.g. an additional pulsation or a leak) can occur and an increased wear of the pump hose has the consequence of a lower reliability in pump operation. In addition, such a solution has a considerably increased constructional space requirement and has a number of additional parts and joints, which are not rotarily movable and which increase the technical effort, impair the appearance (joint appearance), result in abrasion marks at the guides and risks of functional failure (dirt and increasing friction impair the function), make the sealing of the machine space more difficult and result in the risks of clamping. In addition, a pump bed which can be opened as widely as desired cannot prevent the pump hose segment from still being radially outwardly widened in embodiments as a pre-fixed loop due to the rollers moved out up to the abutment and thus from being spreadingly fixed, which only enables the complete installation when using the hands and prevents the dismantling by shape matching and force transmission. The problems with the hose guide wings additionally still result, which bring about the problem scheme already described above.
For this reason, an adjustable pump bed is generally dispensed with and instead the rotor is configured to be adjustable. In this context, an adjustment device is usually provided with an adjustment element by which the position of the hose rollers is adjustable in the radial direction. The hose rollers can thus be pulled through the adjustment device for the secure laying of the hose between the rotor and the hose roller track. The pump hose is hereby geometrically set completely free on installation and dismantling. The problems of a segmented pump roller track are also dispensed with.
In this connection, it is known from U.S. Pat. Nos. 4,568,255 and 5,549,458 to adjust the rollers manually in the radial direction via a rotary knob. Such a manual adjustment possibility is, however, less user friendly and moreover extremely prone to operating errors. In addition, the known manual adjustment possibilities are very complex and/or expensive in construction.
An adjustability of the rollers via a separate adjustment drive is, in contrast, known from WO 95/17598 A1 as well as from U.S. Pat. No. 4,205,948, with here, however, a complicated joint arrangement as well as the complicated adjustment drive arranged outside the rotor being necessary.